Telephone for transmitting and reproducing sounds.



I R.' RUIVIML:ERI I TELEPHONE FOR TRANSMITTING AND REPRODUCING SOUNDS. IAPPLICATION FILED APR. 24. 1914.

lll lil TA BUIDOW Elmll/ILEZR, F -VVILIMILE'T'TPE, ILLINOTS.

TELEPHONE FOR TRANSMITTING AND REPRODUCING fiflmt l.

Specification of Letters Patent. Patented Aug. 2%, 1951?,

Application filed April 5%, 19M. Serial No. 834,093.

To all'whom it may concern:

Be it known that I, Rpnow RUMMLER, a citizen of the United States ofAmerica, and a resident of Wilmette, county of Cook, and State ofIllinois, have invented certain new and useful Improvements inTelephones for Transmitting and Reproducing Sounds, of which thefollowing is a specification.

This invention relates to telephones wherein a diaphragm and coil ofWire are so arranged that the coil mayhaye a direct inductive action onthe diaphragm, more or less independently of the magnet, but includesmeans for magnetically suspending the diaphragm in a magnetic circuitwhich may be independent of or not coextensive with the magnetic circuitof the coil.

The main objects of the invention are to provide a telephone receiver ofrefined construction having great accuracy in sound reproduction andadaptability for long distance transmission. To this end the receiver isprovided with a coil having a direct action on the diaphragmindependently of the magnet in order that the usual iron' losses in themagnet and pole pieces may be avoided, and the device permitted toreproduce sound of any desired frequency without distortion ofthe sounddue to induced currents in the electric circuit, set up by molecularvibrations occuring in the magnet, and to provide a receiver permittingthe use of a permanent magnet of any desired power without subjectingthe diaphragm to a magnetic pull, which would interfere with itsrequired vibrations. Further objects of the invention are to provide amagnetic receiver in which the permanent magnet is not subject todemagnetization by a. current flowing in one direction in the coil.

An illustrative exan'iple or embodiment of this invention is shown inthe accompanyin%drawings, in whichigure 1 is a plan view of a receiverconstructed in accordance with this invention.

Fig. 2 is a sideelevation of the same.

Fig. 3 isa detail in section of the dia- 'phragm.

In the construction shown, an elliptical diaphragm 1 of magneticmaterial, such as soft iron, is shown located above a flat spiralelliptical coil of insulated wire 2, this coil being connected in anyusual manner in the telephone line circuit.- The diaphragm is shownsupported at its endson a permanent steel magnet 53, while the coil 2 isshown sup ported on a suitably formed plate 4 resting on and-secured toinwardly extending lugs 5 of magnet 3. Gaskets 6, shown in section, areinterposed between the ends of the diaphragm and magnet 3 for thepurpose of preventing any interfering sounds due to engagement orrelative movement between I the diaphragm and magnet. The coil 2 ispreferably coated with a dielectric of high inductive capacity adaptedto cement the convolutions of the coil together and also close as muchaspracticable, the air gap tive manner to any slight disturbances.

While all of the useful purposes of a magnet, as customarily employed intelephone receivers, are attained in this structure, the magnet is soarranged with respect to the coil and diaphragm as not to retard thevibration of the diaphragm by attraction, or prevent the full action ofthe current, carried by. the coil, on the diaphragm Without intermediateiron losses. When such losses amount approximately to one watt per cycleper pound of iron, it may be seen that they become very serious ininstruments intended to produce vibrations up to and over 1,000 persecond.

In telephonic work the frequency of voice currents is so high that thereactance of the coil becomes of a relatively high value when the coilhas an iron core, so that there is considerable phase displacementbetween the voltage and the resultant current. the iron is removed fromthe core, the re actance of the exciting coil is reduced, resulting inclearer transmission'values.

The coil 2 may be provided with a soft iron core 7 if desired, but inthat case the operation of the device is altered as the magnetic pull ofthe.coil is increased, say about. eighty times. The last mentionedarrangement. involving magnetic attraction between the diaphragm and thecore of the When coil may be particularly useful in circumv stanceswherein the iron losses in the core and its retentivity may beneglected. For

instance, when vibrations of high frequency and reproductions of greataccuracy are not required. The diaphragm 1 need not be composed entirelyof magnetic material but 'may be compounded with other materials 'havingconstituents including dielectrics,

period of vibration due to its springy char-' acter, llegardless of thesound waves, for instance as would take place if the diaphragm were madeof steel. I

In the operation of the device either as a transmitter or receiver,electromagnetic induction between acoil and diaphragm takes place eitherby movement of the diaphragmunder sound waves or a variable ,currentconducted by the coil. In each case, however, a magnet of any desiredpower is permitted to perform useful purposes Without involving needlessreactance in the coil or interference with the desired operation fromthe result of molecular vibrations in the magnet which occur when it isdirectly connected with the core of the coil. Because of the springycharacter of the material of ermanent magnets, such vibrations when oncesetup persist for some time. and interfere witli the operation of thedevice.

Although but one specific embodiment of this invention has been hereinshown and described, it will be understood that numerous details of theconstruction shown may be altered or omitted without departing. from thespirit of this invention as defined by the following claims.

I claim:

1. A device of the'class described,.com-

prising a vibratable member, a coil of Wire,-

and a magnet, said vibratable memberbeing arranged .in substantialmagnetic suspension in the circuit of said magnet, said coil being solocated that its magnetic circuit is not coextensive with the circuit ofsaid magnet but includes the vibratable member therein.

2. A device of the' class described, com-,

prising a vibratable memberwithout substantial permanent magneticqualities, a coil of wire, and a magnet, said vibratable memher beingarranged in substantial magnetic suspension in the circuit of saidmagnet,

said coil being so located that its magnetic circuit is not coextensivewith the circuit of said magnet but includes the vibratable membertherein. v a

3. A device of the class described, comprising a vibratable member, acoil of Wire,

acore for said coil, and a magnet, said vibratable member being arrangedin substantial magnetic suspension in the circuit of said magnet, saidcoil being so located that its magnetic circuit is not coextensive withthe circuit of said magnet but includes the vibratable member therein. f

Signed at Chicago this 22nd day of April,v 191 I RUDQWRUMMLER.

Witnesses:

ILLIAM E; HANN, EONA SMITH.

